Process of dewaxing oil



Aug. 24, 1943. I E. A. NILL 2,327,445

FROG-E55 0F DEWAXING OIL Filed April 27, 1940 WAXLIKE WAX BEVARING 4 DEWAXING 4 SOLID on. SOLVENT CHILL FILTER W V V I SOLVENT RECOVERY STILL DEWAXED RECOVERED OIL SOLVENT INVENTOR EDWARD A. NILL ATTORNEYS Patented Aug. 24, 1943 UNITED 7STATES "PATENT OFFICE 2,327,445 PROCESS OF DEWAYING on.

. 7 Edward A. Nill, Detroit, Mich. Application April 27, 1940-, Serial No. 332,043

4 Claims. (01. 195-19) This invention relates to a method ofseparating wax from wax-bearing oil, and in particular to a method whereby a wax of superior quality i obtained.

In the refining of parafilne base petroleum the fraction obtained by vacuum distillation, after the light oils have been removed by atmospheric distillation, is a mixture of lubricating oil and a number of waxes. One method for separating the wax from the lubricating oil is to chill the oil to approximately 30 F. and filter the precipitated wax from the mixture. The wax obtained by this method is of marketable quality but the lubricating oil produced has a pourpoint of about 30 F. and must be treated with a substantial amount of an expensive pour point depressor in order to render it suitable for winter use.

Another method for separating the Wax from the oil is to mix with the wax-bearing oil a solvent in which the normally solid and normally liquid constituents of the wax-bearing oil are soluble at elevated temperatures of th order of 100 F., or above, and substantially completely insoluble at temperatures of theorder of F. to

F. This solvent-oil-wax mixture is then chilled to temperatures of the order of and filtered, whereupon an unmarketable, low melting point wax is produced, and by evaporating the solvent from the filtrate a lublicatingbil of low pour point is obtained. 7

It is an object of thisinvention to provide an improved process for separatingthe wax from wax-bearing oil and to produce a superior quality wax.

It is a further object of this invention to provide a process for separating wax from waxbearing lubricating oil, whereby superior quality waxes and low pour point oils are produced.

Other objects and advantages will be apparent from the following description and appended claims.

According to my invention a solid, waxlike compound, such as the hydrogenated fatty acid functional derivatives, is added to wax-bearing oils in the presence of a solvent in which the wax and oil are both soluble at elevated temperatures, but in which the wax is relatively insoluble at low temperatures. The mixture is then chilled at a temperature which may be as high as about 30 F., whereupon a high melting point wax precipitates and may be removed and, upon evaporation of the solvent, a low pour point oil remains. The fatty acid derivative changes the character of the wax in the oil, so that it has a much higher melting point, an increased hardness, a decreased solubility at low temperatures, and crystallizes with crystals which do not inter lock and, on account of their shape, are spaced apart sufficiently to permit relatively free how of liquids therethrough. The increased hardness and higher melting point render the wax suitable for numerous industrial applications in which lower melting point wax is unsuitable. The increased uniformity of crystals and the decreased solubility of'the wax facilitate removal of the wax from the oil. While solid, fatty acid functional derivatives, illustrated by the fatty acid esters, amids, and salts, improve these properties toa certain extent, the hydrogenated glycerides of'solid fatty acids, or admixtures of these substances with metallic salts of solid fatty acids, produce very exceptional waxes and are preferred.

The accompanying drawing is a flow sheet of the method for dewaxing wax-bearing lubricating oil, employing the products of this invention.

Referring more particularly to the drawing, the hydrogenated solid fatty acid derivative, which is capable of raising the melting point of the Waxes and altering their crystal arrangement is added from a container to the wax-bearing oil in a suitable agitator or mixer. The proportions in which the modifying solid can be added to the wax-bearing oil vary; but it is found that by increasing the proportion up to a certain amount for a given oil gives increasingly beneficial results, while increasing the proportion above that amount gives no further benefit. In ordinary cases a percentage of from .5 to 10% (based on the wax in the oil) may be used, and when 2.5% of additive material is used the wax obtained has a melting point of about 143 F., whereas, when 5% of additive material is used, the melting point of the wax cake is about 157 F.

A dewaxing solvent, which, by way of example, may be a mixture of about 1 part acetone and 2 parts benzol, is added to the wax-bearing oil in the proportions of about 1 part oil to 3 parts solvent. The solvent may be any one of those commonly used in the art, such as methylethylketone, acetone-benzol-toluol mixtures, etc., and should be added at a suitable temperature to dissolve all the wax. The oil mixture is chilled in any suitable manner, as by passing through chilling coils, to reduce the temperature, so that the wax may be readily separated from the oil. The wax may be separated in various ways, as by centrifuging or in a filter of suitable construction, such as a continuous or pressure filter. In order to cause precipitation of the wax from the solution, so that it may be readily separated, it, is not so essential, in my process, that the oil and solvent mixture be chilled as low as has been previously necessary to cause precipitation of the wax. For example, chilling to a temperature of about 30 F. is usually sufficient. However, it may be chilled even lower than 30 F. without am! deleterious efiects. The solid wax, either removed from the filter or while remaining in the filter, may be washed with an additional quantity of solvent, which has also been cooled to a similar low temperature, to remove any entrapped lubricating oil. The dewaxed liquid is then passed through a solvent recovery still, where the solvent is recovered from the dewaxed oil and stored or returned for reuse in the process. The dewaxed oil is of low pour point.

Although one may prepare a low pour point lubricating oil and a high melting point wax by the process outlined above, circumstances may be L such that it is undesirable to alter existing apparatus'sufiic-iently to use the dewaxi-n gsolvvent. In such cases the hydrogenated soli-d fatty acid derivatives are dissolved in the wax-bearing oil and the mixture chilled suiiicient-ly to precipitate the wax, which is then separated from the oil and purified by any conventional process; iorexample, by the well-known sweating process. The :oil which is obtained directly from the filter has a higher pour point thanoii obtained when the' deare all suitable for use in the process. The compositions containing metallic salts of fatty acids mixed with hydrogenated glycerides are preferable for the reason that the effect on the melting point of the wax produced .is more pronounced.

It has been found that the hydrogenated glycerides of the solid fatty acids are very eifective in producing higher melting points. As these are readily obtainable they are usually preterable for use in the process.

The pou-r point of the oil produced by-thisprocess is considerably lower than :the temperature at which precipitation of the wax-occurs. It is accordingly apparent that the addition of the above materials to the wax-oil mixture permits the wax to be extracted at higher temperatures, a condition which efiects great economy in the refrigeration process. y producing wax or more unifor-m structure the filtration and separation of Wax are greatly facilitated.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and, therefore, only such limitations should be imposed as indicated in the appended claims.

What I claim is:

1. In a process for separating wax from waxbearing lubricating oil wherein the Wax-oil mixture is chilled to solidify the wax, the step which comprises incorporating in the wax-oil mixture, before chilling and in the presence of solvent which is liquid at atmospheric temperatures, a hydrogenated solid fatty acid glyceride.

A process for producing low pour point lubricating .oil from wax-bearing oil, which comprises dissolving in the wax-bearing oil a hydrogenated solid fatty-acid glyceride, adding to the Wax-bearing oil a solvent for the oil and wax in which solvent the wax is soluble at high temperatures of the order of 100 and relatively insoluble at a temperature of 0 R, chilling the mixture, separating the wax from thesolvent oil mixture, :and evaporating the solvent from the oil.

3. In a process for separating wax from waxbearing lubricating oil wherein the Wax-oil'mixture is chilled to. solidify the wax, the step which comprises incorporating in the wax-oil mixture before chilling and in the presence of a solvent which is liquid at atmospheric temperatures a hydrogenated solid fatty acid glyceride and a metallic salt of a fatty acid, whereby the melting point of the Wax separated is higher than that obtained when only the hydrogenated glyceride or wax is used and whereby the tensile straigth and grain structure of the wax obtained are greater than that of wax separated irom the some oilwith either said glyceride or saidisoap alone.

4. In a process .ior separating wax from waxbearing lubricating oil wherein the wax-oil mixture is chilled to solidify the wax, the steps which comprise incorporating .in the wax-oil mix'tm'e before chilling and in the presence of a solvent which is liquid at atmospheric temperatures a metallic salt of a. higher fatty acid and a hydrogenated solid fatty acid glyceride to improve the efiiciency of th separation of the wax from the oil and to procure a wax that has a higher melting point than has wax separated from the same wax-oil mixture with the aid of a natural glyceride in place of said hydrogenated glyceride.

EDWARD A. NILL. 

